Power plants or industrial plants perform periodical inspections in order to maintain the safety and reliability of equipment. In particular, visual inspections (VT) are frequently used for ease of inspection. For example, the visual inspections have been frequently used where in a nuclear power plant, a remotely-operated camera is used to take an image of an inspection target and the image is displayed on a monitor so that an inspector can visually confirm the image (Patent Document 1). The purpose of the method is to suppress the number of people (workers and inspectors) working in a radiation control area of the nuclear power plant and to shorten the working hours thereof.
Further, there has been invented a method of obtaining a wide range of image data by scanning images inside a wide range of a large facility such as a nuclear power plant using an inspection apparatus mounting a plurality of cameras (Patent Document 2).
Furthermore, the present inventors have developed and disclosed a shroud automatic inspection apparatus which automatically detects a shroud defect inside a nuclear pressure vessel (Patent Document 3). The shroud automatic inspection apparatus is configured such that a sensing device moves above a shroud surface to take an image and the image is inputted to an image processing device; the image processing device performs image processing on a picture signal from the sensing device; if the shroud is assumed to have a defect, the image processing device calculates the 3D (three-dimensional) shape of that portion; and a flaw detector further calculates the detailed three-dimensional shape of the defect. The shroud automatic inspection apparatus can automatically detect any defect from the continuously fed shroud images and can detect a more detailed three-dimensional shape of the detected defect portion.    Patent Document 1 is Japanese Published Unexamined Patent Application (Patent Laid-Open) No. 2000-346976 (JP-A-2000-346976);    Patent Document 2 is Japanese Published Unexamined Patent Application (Patent Laid-Open) No. 2002-149859 (JP-A-2002-149859); and    Patent Document 3 is Published Unexamined Patent Application (Patent Laid-Open) No. 11-326580 (JP-A-11-326580).